الفهرس 
Acknowledgements
Salifa perspicaxOnly 14 pages are availabe for public view
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Abstract
- In the present study, the nervous system of four species of leeches; Barbronia assiuti, Salifa perspicax, Salifa delicata and Helobdella conifera were studied.
- The nervous system of the four leeches consists of a supra esophageal ganglionic mass, two circum-esophageal commissures, a sub pharyngeal ganglionic mass, a ventral nerve cord with 18-21 free ganglia which differ from species to another.
- The supra esophageal ganglionic mass forms a small brain above the pharynx in segment V. It consists of two fused ganglia.
- The sub esophageal ganglionic mass lies ventrally below the pharynx in segment VI. It consists of four fused ganglia.
- Terminal ganglionic mass show different number of fused 7-10 ganglia according to species.
- The ventral longitudinal nerve cords consist of two longitudinally extending axons, fibers and a median Faivr,s nerve.
- The nervous system of studied leeches was surrounded by ventral haemocoelic sinus.
- The nervous tissues were surrounded externally by connective tissue capsule and lining from inside by inner capsule.
- Ganglia contain packets of nerve cells which differ from species and from region to another.
- The nerve cells were classified into three types, which differ in shape, size and intensity of cytoplasm.
- Type A cell had the smallest surface area and the largest numbers comparing to type C and B.
- The neuroglia cells can be classified into micro and macro glial cells.
- In the studied leeches a limited number of macroglia was present in each ganglia and connectives in fixed sites.
- Microglia cells were distributed in large number in the ganglia and connectives.
- The nerve cells had a good amount of free ribosomes, polysomes and large numbers of electron dense particles.
- A cell type had intense basophilic staining due to the presence of a good amount of RNA.
- B cell type in Barbronia assiuti had electron dense cytoplasm in the supra and sub esophageal ganglia while in caudal ganglionic mass they acquire electron lucent cytoplasm.
- C cell type in B. assiuti showed three different structural phases.
- The surface area of ganglia differs from species and from region to another.
- In the present work, the largest nuclear cytoplasmic ratio (n/c) was recorded in A cell, B cell and C cell in B. assiuti, S. perspicax and H. conifera and S. delicata respectively.
- The nervous system of Salifa delicata and Salifa perspicax showed no clear differences concerning the anatomical and histological studies.
- The present study suggests that the histological structure of the nervous system of the different species of leeches is useful and interesting.